This invention involves devices such as that shown in U.S. Patent application Ser. No. 237,889, entitled Detenting Lift Cover, Ehrenfels et al, filed Feb. 25, 1981, which involved a generally cylindrical housing for receiving a receptacle or other electrical wiring device which in intended for use in environments where it is subject to undesirable, extraneous matter.
In that application there is disclosed a wiring device housing having a rim or flange at its open end, the flange having thread-like camming surfaces. A cover is hingedly connected to the housing by a L-shaped arm, one end of which is pivotally attached to the exterior of the housing and the other end of which is coupled to the center of a generally circular cover in a manner permitting the cover to be rotated relative to the arm and the housing. The cover has a skirt extending axially toward the housing when the cover is closed, the inner diameter of the skirt being larger than the housing flange. Mating cam surfaces are formed on the skirt so that, after the cover is closed, it can be rotated to engage the cam surfaces and lock the cover tightly in place.
In order to complete the sealing of the housing and protect the interior thereof from extraneous foreign matter, such as water, rain and solid particulate matter, an elastomeric seal is adhered to the inner surface of the cover, the seal being positioned and dimensioned to abut the axially facing distal surface of the housing. The seal is commonly a flat, annular ring of spongy, rubber-like material which is compressed between underlying surfaces of the cover and housing, respectively, when the cover is closed to effect the sealing of those surfaces.
It has been found, however, that under some conditions the seal frictionally engages the abutting housing surface and resists sliding as the cover is rotated. Particularly when the coefficient of friction increases as the result of high temperatures or foreign particulate material in the housing or imperfections in the housing, the seal "grabs" the underlying housing surface upon cover rotation and may be pulled away from the underlying surface of the cover or wrinkled or folded, especially after repeated openings and closings of the cover. Thereafter, the seal does not seat properly, interrupting an otherwise continuous seal. In extreme cases, the seal can even be pulled completely loose and lost, in which case the capability of the wiring device to prevent entry of extraneous foreign matter is seriously diminished.